Theme 5AB Flashcards
Patterns in Nature
- Evo produces 2 patterns - Nested similarities found amount extant species + historical pattern recorded by fossils
Phylogeny
- History of descent with branching
- Much like the genealogy in our own family history
- Way of organizing our knowledge of biodiversity
Phylogenetic trees/Phylogenies
- Branching diagram that shows relationship b/w species according to the time since a common ancestor
- Shows which other species/group of species it shares its most rcent common ancestor with
- Provides hypothesis of evolutionary relationships
- Represent best model of relatedness of organisms on the basis of data
- Can show branching patterns of lineages, not just species
Parts of Phylogenetic Tree
- Image taken in photos
- Tips, branches, nodes, root, time(?)
Sister groups
- Two species (or groups of species) that share common ancestor not shared by any other species or group
Equivalent Trees
- All the same
- Nodes can be rotated without changing evolutionary relationship
Phylogram
- Tree where branch lengths represent amount of inferred evolutionary change/time
Cladogram
Tree where all branches equal length
Monophyletic group
- Clade, includes a common ancestor and all its descendents
Frogs, salamanders, caecillans all amphibians
Parapyletic group
- Includes a common ancestor andsome, but not all, of its descendants
Turtles, Lizards & Snakes, Crocodiles & Alligators all reptiles
Polyphyletic group
Doesn’t include common ancestor
Bats and Birds both flying tetrapods
Shared Characters
- Phylogenies inferred using characters that’re shared b/w species
- Characters used: Vary among, but not within species & have a genetic basis
- Morphological (wing pattern)
- Chromosomal (# of chromosomes)
- Molecular (DNA sequences)
Characters: Morphological or DNA
- Observable triats of the whole organism
- Evidence is a character with a # of discrete character states
- I.e. Flower colour (character): Blue, yellow (State)
- Wings: Present, absent
Homologous Characters (Homologies)
- Shared cuz of common ancestry
- Shared ancestral & derived characters
Analogous characters (homoplasies)
- Homoplasy means similarity in appearance but not in origin
- Shared cuz of convergent evolution
Phylogeny Reconstruction
- Homologies recognized by - Structural similarity, relationship b/w parts, embryonic development
- Strongest hypothesis of evolutionary relationships is tree with fewest # of changes required
Derived Character
- Unique character states uninformative for sister group
- a trait that arose in most recent common ancestor of particular lineage and was passed along to its descendants
Synapomorphies
- Need homologies shared by some, but not all
Most likely phylogenetic tree
- Fewest # of changes required often favoured
- Most parsimonious best
Parsimonious - Phylogeny requiring fewest evolutionary changes is the best estimate of the true phylogeny
Molecular data complement comparative morphology
- Each nucleotide in DNA sequence can act as trait
- Amino acid sequence of proteins can work the same way
- Underlying logic of phylogenetic inference is identical for morphological & molecular characters
Distance method
Alt method of reconstruction
- Infer relationships from actual data - descendants of recent common ancestor will have had little time to evolve difs, descendants of ancient common ancestor = more time
- DNA sequence difs reflect time since common ancestor
- Therefore, can estimate degree of relatedness from comparison of DNA sequence
Macroevolution
- Evolution above the species level
- I.e. Assess the diversity of an entire clade & its position on the tree
- Includes adaptive radiation, anagenesis, cladogenesis
Adaptive Radiation
- Rapid evolution of new species occupying new niches
Anagenesis
Speciation wherein the ancestor species is wholly replaced by new species
Cladogenesis
Parent species splits into 2 species
Graduated Evolution
Slow & steady gradual evolution (results in more anagenesis)
Punctuated
Rare & rapid (on a geologic time scale) events of branching speciation (results in more cladogenesis)
